As mobile phones have become more sophisticated, mobile phones in which the housing is composed of two parts in order to arrange various components have become the mainstream. In such mobile phones in which the housing is composed of two parts, they are held in a state where one housing is placed on top of the other housing when they are in a standby status, and then desired components are exposed by opening one of the housings when they are used. One of the opening methods for these housings is a semiautomatic sliding method. In a mobile phone using a semiautomatic sliding method, when sliding of the housing is manually performed to a certain position, the housing is automatically slid to a predefined state even if the hand is taken off the slide, and thus providing enhanced usability. In general, a sprig is used for this semiautomatic sliding method. Patent document 1 has realized a semiautomatic sliding structure by guiding both ends of a helical spring provided on the upper housing along a straight guide rail and a convex-shaped guide rail provided on the lower housing. In the mobile phone of Patent document 1, after the housing is slid manually so that one end of the helical spring is moved to the crest of the convex-shaped guide rail while the helical spring is expanded, the housing is automatically slid to a predefined position by using the contracting force of the helical spring even if the hand is taken off the housing.    [Patent Document 1]    Japanese Unexamined Patent Publication Application No. 2006-186201